Welcome to the board, Marie.
Freestyle embroidery designs can be either traced onto a piece of fabric from any design you wish, or you can buy pre-designed linen with the design stamped onto it. This pre-done stuff is usually doilies, runners, tablecloths, etc.
DMC has a nice range of these, and your local embroidery shop should stock them. (Look for them under the name "traced linen")
As for doing the design yourself, a favorite sourcebook that I use is "Designs and Patterns for Emrboiderers and Craftspeople" by Marion Nicols and published by Dover.
Don't be held back, however - colouring books are great places to find good designs as well.
This is well named Freestyle embroidery, because the only limit you have as far as design and stitches is your imagaination and skill.
A word on fabric choice: DON'T USE AIDA! For this type of embroiodery you need a tightly woven fabric - dress linen is ideal, as is calico or heavy cotton. Use a Crewel embroidery needle for preference (I prefer a size 10) although a fine hand sewing needle is also ok.
This is my favorite style of embroidery!
I hope that this helps!